热锻温度对模具修复层组织性能的影响

Effect of Hot Forging Temperature on Microstructure and Properties of Die Repairing Layer

通过对覆层用Deform-3D的模拟、金相实验和硬度测试,分析了热锻模具修复层温度变化规律以及组织和性能变化。结果表明:锻模工作过程中循环升温和降温速度较快,有利于碳原子和铁原子的扩散,覆层发生反复的回火再结晶,晶粒平均尺寸长大到180μm。微观组织由回火索氏体+下贝氏体+回火马氏体(平均硬度530 HV)转变为回火索氏体+贝氏体+合金碳化物Cr7C3、Mo2C形成的机械混合物,导致表层的强度严重下降,塑性韧性有所降低。

Through simulating overlying layer with Deform-3D, metallographic phase experiments and hardness testing, the change regulation of temperature of hot forging die repair layer and its variety of microstructure and properties were analyzed. The results are as follow： the faster cyclic heating and cooling speed in the forging die working process benefit diffusion of carbon atoms and iron atoms. The annealing recrystallization occurs in overlying layer, and the average grain size grows up to 180 v^m. Microstructureis transformed from tempering sorbite ＋ lower bainite ＋ tempered martensite （the average hardness of 530HV） into the mechanical mixture of sorbite ＋ bainite alloy carbides Cr7C3, Mo2C, which leads to the surface strength seriously descending and plastic and toughness decreasing.